I need help deciding what to do...4.1 built or 3.8 built

[rayray231]

iam also building a 4.1 and you can get crank rods and pistons for around $ 1,600 thats new cat crank, k1 rods, and wesico pistions. I think its like 272 c.i. it dosen's require as much grinding of the block. Due to marriage trouble havent made any progress on new engine in a while but soon to resume i am going to use the ported iron heads and champion intake so i need to work out the fuel system and for the turbo i have obtained a pt6776 bb, RJC front mount, does anyone have suggestions on a fuel system?

 

[SVT F15O]

4.1L all the way!
I have already pushed my stock crank/rod 4.1 to a 10.35. Should have gone faster last year but I had tranny issues.
The motor is out right now for a stroker Cat crank and K1 rods. Also gonna do a turbo change. I am shooting for 9's on 93 octane and Meth.

 

[SHADOWII]

The block#...

I have is not the 484 or the 291, it's a 553 However, next to the sg-1, it looks almost the same except for the missing holes(oil return, knock sensor, and the perferated valley of course) There's no cracks in the deck, and they appear to have the same deck thickness. the ribbing is thicker than the sg block. Can't find a reason not to use it. I believe this the block used by cadillac.

 

[49-blues]

I believe that is also a good block to use. do you have some pics of the valley?

 

[DCG]

3 way conversion

I have hot air 3.8L motor I bought to do the 86-87 conversion on, but after reading this post now I want to do the 4.1L. Is the 4.1L block stronger than the 84-85 hot air 3.8L block? Could I use the 84-85 rotating assembelly (except for pistons), oil pan, 8445 heads, front cover, and all the external parts from the 86-87 to make this work. I read the links above but still don't understand which 4.1L block is the best? Anybody have any power estimates with the te 44 turbo, 36# injectors, stock intercooler with dutt neck, and all the stock 86-87 parts. Could I get away with not porting the heads, and not doing the griddel on the bottom end. I am trying to do it on a budget. Car is street driven with moderate boost levels(18-20 psi). Maybe taken to the strip a few times a year.

 

[49-blues]

I would say both blocks are probably equally as strong as each other,however that is why you can strengthen them with studs,caps etc.

 

[boostingbuick]

My deck is cracked. My old 4.1 deck was cracked. I have had no issues with the crack and will keep trying to kill it till something lets go. I knew it was cracked when I started this build of my current engine. For what its worth, I think the crack has nothing to due with anything, no leaks or concerns.

 

[boostingbuick]

and my engine is bored to 4.030.

 

[Black Power]

and my engine is bored to 4.030.

I am glad you post up about your 4.1. You have been my inspiration for my buildup. I started building mine thinking the deck was crack free but as I started to put it together yesterday I saw 2 really thin hairline cracks in the deck from the water jackets to a head bolt hole, and it looked like another was going down the same road.

I left the shop and came home to look up some of your posts, I thought you had the same cracks and you were still going strong. Did you helicoil the holes or anything? Head studs, stock bolts, or ARP bolts? How much boost and what turbo are you running on that little monster?

Sorry for all the questions. :biggrin:

Edit, oh I see, 72mm BB turbo...

 

[joe_schindler]

Build what you have the most pieces for. The difference is probably pretty small. If you've got most of a 4.1; there's not much down side.

 

[coldair85GN]

I dropped my 4.1 off at a machine shop yesterday afternoon for a dip in the tank and then a magnaflux/sonic test. The owner of the shop took a quick visual and was not real positive about what he saw. He estimated it would take a 40 over bore to be usable and I am concerned about going that far into this block considering my goals.

 

[Black Power]

dude that thing would have to have a LOT of cylinder wear or maybe some nasty ass rust for it to need a .040... Mine cleared up on a .020 (except one hole) so I bored it to .030, and I thought it had a lot of wear...

 

[coldair85GN]

NASTY NASTY Rust. Looks like it sat uncovered for a LONG time.

 

[87buickracer]

X2

3.8 with girdle here!!Best way to go!!
Use 4.1 for stock rebuild..

 

[dlafont]

If you want to use the Hyper pistons (4.00" bore) you will need to bore out 0.035. Maybe you can get away with 0.035?

 

[coldair85GN]

still waiting to hear from the machine shop. If I went to a 4.0 bore I could use small block chevy pistons...I guess that might be a plus to going that large..it would make finding pistons easier

 

[boostingbuick]

No heli-coils. Just ARP head studs.

And mine is bored to 4.030 which makes it .065 over. So that makes it weak??? I wish someone could tell me why not to run this engine. The only way to tell how think the cylinders walls are is to sonic check the walls.

Full stock weight and 128 on 93 is making some power, and yet it still runs.

 

[Black Power]

No heli-coils. Just ARP head studs.

And mine is bored to 4.030 which makes it .065 over. So that makes it weak??? I wish someone could tell me why not to run this engine. The only way to tell how think the cylinders walls are is to sonic check the walls.

Full stock weight and 128 on 93 is making some power, and yet it still runs.

I am going to do what you did, except littler turbo and I am not going to go as fast as you. I am shooting for some low 12s or high 11s and driving it all the time

 

[Powder]

While rummaging through some old literature in my vast collection this morning I came across an old article about a stage II 4.1 built and raced by Lou Czarnota of Lou's Auto Service,(a vendor). This engine had twin turbos and was in the 1K HP area. You might call him and get his professional take on the pros and cons of a 4.1 for your application. If he doesn't know, who would?:biggrin:
MLH

 

[boostingbuick]

This a touchy subject for many people, but mostly a lot of speculation. I feel if you don't have first hand knowledge of this then stay out it. I feel that can mislead people who have blocks that want to do something with it or to obtain one. I have had two 4.1 and been fast with both of them. Much faster if I took some weight out.


Now I have talk to one person with a bad experience and will not say that the 4.1 is the answer to all of problems. They are still a production base engine that I have made good power with. And they are not for everyone. But I am one who still runs one and will say that I will not go back to a 3.8 unless something drastic happens.